Fabric conditioning compositions are often used to deposit a fabric softening compound onto fabrics. These are usually rinse added fabric conditioning compositions. Typically, such compositions comprise a fabric softening agent dispersed in water. The fabric softening agent may be included at up to 7.5% by weight, in which case the compositions are considered dilute, or at levels from 7.5% to 60% by weight, in which case the compositions are considered concentrated.
It is obviously highly desirable for any fabric conditioning composition to provide excellent softening. It is known that better softening can be achieved using saturated (i.e. hardened) softening compounds instead of unsaturated or partially unsaturated softening compounds.
Hardened softening compounds are also believed to have less base odour than unsaturated softening compounds. Therefore, it is desirable that any fabric conditioning composition comprises hardened or substantially hardened softening compounds.
The inventors have now found that saturated quaternary ammonium fabric softening compounds based on triethanolamine (TEA) have lower melting temperatures than commercially available saturated softening compounds such as 1,2 bis[tallowoyloxy]-3-trimethylammonium propane chloride and N-N-di(tallowoyloxy ethyl) N,N-dimethyl ammonium chloride.
It is particularly desirable that the fabric conditioning composition should comprise a low melting point softening compound as this improves the ease of processing of the softening composition as well as the eventual formation of the aqueous dispersion. Thus, it is desirable to use saturated TEA-based fabric softening compounds in fabric conditioning compositions.
However, the inventors have found that concentrated compositions comprising saturated TEA-based fabric softening compounds suffer from viscosity instability (thickening) upon storage, especially at high temperature, e.g. above 30° C.
Instability can manifest itself as a thickening of the composition. This thickening can occur to a level at which the composition is no longer pourable or dispersible in use, and, can even lead to the formation of an irreversible gel. Such thickening is very undesirable because the composition can thereafter no longer be conveniently used, for example unpleasant residues can be left in the dispenser drawer of the washing machine and/or it is unattractive to the consumer.
However, high temperature storage stability is particularly desired by consumers.
It is known that fatty acids can reduce viscosity (by reducing the size of particles in the composition) as can inorganic and organic electrolytes. However, the inventors have found that none of these provide long term stability benefits for conditioning compositions comprising hardened TEA-based softening compounds.
Thus it is desirable to provide a fabric conditioning composition comprising hardened TEA-based fabric softening compound which overcomes the problem of high temperature instability.
WO 97/16516 discloses a softener composition comprising a cationic softener and a nonionic surfactant in a ratio of 1:2 to 4:1.
EP 640121 discloses a composition comprising a diester quat and 0.1 to 30% of a viscosity/dispersibility modifier. There is no mention of hardened softening compounds.
EP 734433 discloses mixtures of hardened and partially unsaturated ester quats. There is no mention of nonionic stabilising agents.
GB 2170829 discloses compositions comprising quaternary ammonium compounds and fatty alcohols in a ratio of 6:1 to 3:1. There is no mention of the iodine value of the quaternary ammonium compound.
WO 99/29823 discloses a process for making a softener composition comprising forming a melt of a softener and optional additives, dispersing this in water, cooling to below the Krafft temperature of the softener and adding dye and nonionic material. There is no suggestion that the nonionic material can be incorporated before the mixture cools. Furthermore, there is no reference to high-shear milling.
EP 503221 discloses a composition comprising a cationic softener, a linear fatty alcohol ethoxylate and a highly branched fatty alcohol. There is no mention of a hardened cationic softening compound.
EP 309052 discloses a composition comprising 11 to 25% of a quaternised ester-amine, 0.1 to 10% of a linear alkoxylated alcohol with 1 to 10 alkylene oxide groups and 60% or more of a liquid carrier.